Process for sensitizing dyestuffs employed in photography.



.ronn' n. srrrrn, or nors-coroirrnns, rrrcn.

PCESS FOR SENSITIZING' DYESTUFFS EMPLOYED IN PHOTOGl-PHY.

lldlddfidd.

111' 0 Drawing.

To all whom it may concern:

Be it known that I, JOHN H. SMITH, a citizen of the Republic of France,residing at Bois-Colornbes,- France, have invented new and usefulImprovements in Processes for sensitizing Dyestufis Employed inPhotography, of which the following is a specification.

.lln connection with the bleach-out process of color photography it hasbeen the aim of investigators to discover more energetic sensitizers forthe bleach-out dyes than those already employed, both with the view toshortening the duration of printing and with renderingavailablebleach-out dyes of a somewhat faster or more permanent nature under theaction of light in order that the finished prints may be of a morepermanent character after the sensitizers have been removed.

The object of the present invention is to provide a sensitizer for thebleach-out dyes used in color photography which will be more powerfulthan those heretofore in use, which will constitute a more energeticsensit-izer for bringing about a more rapid development of prints andwill furnish prints of a more permanent character.

As the result of extensive experiments, I

have discovered that thiosinamin or allylsulphourea is a much moreenergetic sensitizer than any of those hitherto used or known, it havingfor some dyes a sensitizing action twenty times greater than that ofanethol, the sensitizer which has heretofore been most used andrecommended as yielding the best results as a sensitizer for bleachoutdyes.

1n addition to the powerful action of this sensitizer, thiosinaminpossesses the further advantages of being almost odorless and amenableto employment in aqueous as well as in alcoholic solutions. Thiosinaminmay either be added directly to the photographic emulsion or it may bebrought into combina' tion with sensitive dyes by a subsequent process,such as the bathing process.

Specification of Letters Patent.

Patented Mar. to, are.

Application filed February 15, 1910. Serial No. 544,717.

l have also found that a very large number of dyes are rendered moresensitive to light by the addition of thiosinamin, for instance,methylene blue, Victoria blue, eryt-hrosin and eosin, Thiosinamin alsopossesses the advantage, that it may be emsions, seven parts thiosinaminare employed to one part of the dye, and in silver haloid solutions,equal quantities are used. 8% solutions of the thiosinamin are made useof in preparing the sensitizer in the above proportions.

The term sensitiveness as used in this specification is meant primarilyto indicate the speed with which the dyes fade, or the impulse whichinduces the fading of the d es.

Having fully and clearly set forth my invention, I claim:

1. A process for increasing the sensltiveness to the action of light ofdyestufi's used in photography, consisting in lntroducing thiosinamininto the photographic product containing the light sensitive dye.

2. A process for increasing the sensitiveness to the action of lightdyestufis used in photography, consisting in incorporatlng thiosinaminin the finished photographic product containing the light sensitive dyeand silver haloid. I

The foregoing spec1ficat10n signed at Paris, France, this third day ofFebruary, 1910.

n3. JOHN nsnrrrr.

lln presence (if- H. C. Coins,

Jeers H. Barren.

